I believe that rather than turnstiles, which as you indicate, are probably inacurate due to folks playing with them, that park has a different method fo performing rider counts.
Quite simply on a coaster, they count the *EMPTY* seats that go out on a train, and a count of the number of dispatches during that time frame.
So lets say there were in an hour 20 dispatches, and the "Empty Seat" handcounter read 50, they would take 20 dispatches * 36 seats - 50 empty seats to get 670 riders during that time frame.
On a couple rides they do have turnstiles, these would be: Scrambler, Monster, Troika, Voyager VR, Train Ride.
The Train ride is the real oddball in the group, as there are two stations, Rivertown and Waterworks. Of the two stations the only turnstiles are at the entrance to the Rivertown station, there are no turnstiles in the Waterworks station.
Mind you there are turnstiles to the entrance to Waterworks but they would also count those who opted for the walkway.
Other rides use hand counters and a logbook. I'd say that on most of the rides the handcounter method would be sufficient, except on rides with multiple entry points, such as the queue gates on a coaster, or the multiple gates to the train ride, or Viking Fury. I rekon Viking Fury also uses the empty seat method.
Getting back to the train, I wonder how and if they count it. The mass entry is too heavy for handcounting, and they don't really look too hard at the coaches enoguh to count either way. The turnstiles whould only catch those departing from Riverrtown.
However in the heck the count their riders, they still deserve some kudos for awarding the 1,000,000th rider.